The present invention relates generally to collision avoidance systems and more particularly to a power management scheme for dedicated short range communications collision avoidance systems.
In recent years, safety systems have been developed to assist drivers in avoiding impending accidents, such as collision avoidance and warning systems. These systems may employ direct vehicle-to-vehicle communications or use roadside-based networks to assist or control the vehicle communications.
For example, U.S. Pat. No. 7,315,239 discloses a collision avoidance system. A subject vehicle is provided with forward and rear-ward looking radar systems to determine the speed and relative distances of surrounding vehicles, such as vehicles in front of and behind the vehicle. If a surrounding vehicle comes too close to the vehicle employing the collision avoidance system, the collision avoidance system alerts the driver of the subject vehicle. Additionally, if the surrounding vehicles utilize a similar collision avoidance system, the collision avoidance systems can communicate with each other so that multiple vehicle drivers are simultaneously warned of an unsafe condition.
Intersections are areas of increased collision risk. A collision avoidance system for use at intersections is disclosed in U.S. Pat. No. 7,209,051. A system is deployed at an intersection to assist vehicles in or approaching the intersection. The system utilizes a number of sensors positioned around the intersection. A vehicle sensor monitors vehicles approaching the intersection. An entering vehicle sensor detects a vehicle waiting to enter the intersection, such as by pulling into a gap in the oncoming traffic. The information provided by the vehicle sensor is used to estimate the length of the gap in the oncoming traffic. The system can then inform the waiting vehicle driver when the gap is sufficiently large for safe entry into the intersection.
In the U.S., the dedicated short range communications (DSRC) protocol for vehicle-to-infrastructure and vehicle-to-vehicle communication is becoming a standard technology. DSRC can be used in many applications, including automatic toll collection, traffic management systems, and collision avoidance systems. DSRC systems can transmit vehicle safety messages which account for factors such as vehicle speed, heading, location, and the like and consume up to two (2) watts of power for a transmission according to the United States Federal Communications Commission (FCC) regulations. This large transmission power enables a wide range of communication for the vehicle system. However, the wide range of communication performance also requires stronger computing power (by the on-board computers) to track all of the detected vehicles. Such power consumption is not needed at all times, but current systems do not employ power management strategies. In particular, the collision avoidance system could be operated at less than full power under normal conditions and at full power only when in or approaching a increased-risk location. One such increased collision risk location exists at intersections.
Therefore, there exists a need in the art for a collision avoidance system that manages transmission power based upon a detected collision risk scenario.